/**
 * Created by forcht on 2018/4/28.
 */
public class Solution {
    public int climbStairs(int n) {
        if(n==1)return 1;
        if(n==2)return 2;
        int[] dp=new int[n+1];
        dp[1]=1;
        dp[2]=2;
        for(int i=3;i<=n;i++){
            dp[i]=dp[i-1]+dp[i-2];
        }
        return dp[n];
    }
}
